1. Field of the Invention
The present invention relates generally to an enzyme immobilizing carrier which is used as a bioreactor, biosensor, filter, and so on to facilitate various biochemical reactions in an industrial field which employs various enzymes as a biological catalyst. More particularly, the present invention relates to a porous powder material to produce such enzyme immobilizing carrier, especially a porous carrier. Furthermore, the present invention relates to a method of producing such porous powder material.
2. Description of the Prior Art
In order to execute various biochemical reaction in an industrial field by using an organic catalyst, for example an enzyme catalyst, many researches and studies on an enzyme immobilized bioreactor and a biosensor have been actively carried out in recent years. On the same occasion, studies on an enzyme immobilizing carrier which is applied to these bioreactor and biosensor have been also progressed. Such the enzyme immobilized bioreactor includes a column which is filled with an organic catalytic material made of an enzyme immobilized carrier. For the carrier, various materials may be used, for example high molecular organic materials such as cellulose, agarose, chitin, carrageenan, poly acrylamide, and inorganic materials such as commonly used porous glass, ceramics, and so on.
However, such organic materials are apt to have a poor mechanical strength, and mostly require a high temperature treatment in order to prevent the contamination of various germs in a reaction system employing the above described enzyme immobilizing carrier. The organic materials are easily affected by such high temperature treatment so that their mechanical and chemical properties after the treatment will become unstable. Particularly in a case of mass production system, the organic material carrier will be remarkably compressed by various pressures and therefore the compressed carrier cause fluctuation in reactant flow and pressure. This fluctuation will not perform reaction at a constant rate.
On the other hand the above described porous glass is possessed of an excellent thermal stability and pores having the diameter range of several hundreds angstroms, while its manufacturing process is complicated and requires a fusing step at a high temperature (about 1500.degree. C.) thereby increasing manufacturing cost. This costly process may no be applied to a commercially available plant for lack of economical profit.
When the carrier is produced by a generally used ceramics material as alumina and zirconia such the ceramics carrier has superior thermal and chemical stabilities but less pores having the diameter range of several hundreds to thousands angstroms which are necessary to immobilize the enzyme. Thus the reaction plant employing this ceramics carrier may produce a small amount of the immobilized enzyme and need a relatively large scale and a long reaction period.
Some conventional arts have been proposed to overcome the above described problems caused by using the ceramics carrier. For example Japanese Patent Application Laid-Open Publication No.63-91083/1988 discloses one typical process that some amount of sepiolite as a raw material is ground into grains having a constant particle size, and then the grains are heated at the temperature range of 800.degree. C. to 1000.degree. C. to form a sepiolite based enzyme immobilizing carrier, hereinafter this will be referred to as "sepiolite carrier". Thus produced sepiolite carrier has various merits such as an excellent thermal stability, and many pores having the diameter range of several hundreds to thousands angstroms which are necessary to immobilize enzyme. These pores improve the capability of the enzyme immobilizing function in comparison with the above described ceramics carrier.
Although the sepiolite carrier has the above described merits, the pores are difficult to control as to their distribution and amount. In addition to this problem, the sepiolite raw material contains some impurities such as carbonate minerals, for example dolomite (CaCO2.MgCO3). Since the sepiolite crystals may be broken by any acid treatments for removing the impurities, these alkaline impurities can not be completely removed from the produced sepiolite carrier. When the sepiolite carrier is used as the bioreactor, the alkaline impurities may be eluted under a specific condition and the eluted alkaline components may disturb the biochemical reaction.